To analyze and solve the broadband oscillation problem brought by large-scale offshore wind power access to the power system, this paper develops an offshore wind farm broadband oscillation risk assessment application based on the CloudPSS platform, and realizes a broadband oscillation risk assessment of large-scale wind power grid-connected system based on full electromagnetic transient (EMT) simulation. In addition, a broadband oscillation risk assessment was carried out for a real offshore wind farm, and the simulation result shows that there is a high frequency resonance risk in this offshore wind farm. After adding filter capacitors to the converter controller, the oscillation risk was significantly reduced.